Until
Mount Saint Helens in 1980, Mount Lassen in California was the most recently
active volcano in the United States. It violently erupted in 1914-15 and
sporadically until 1917.

Left
and below: views on the road south from Manzanita Lake.

Bumpass Hell

A
miner nicknamed for an unusual anatomical quirk reputedly discovered this
geothermal area on the east flank of Mount Lassen.

Left: view to the east.

Below: fish stocked in one pond fed by hot springs
grow fat and lazy.

Snow
in August on the summit trail.

Along Highway 44

Mount
Lassen is hardly visible from the approach on highway 44 except for some
ranch clearings a few miles west of the park entrance.

The Devastated Area

The largest eruption in 1915 set a surge down the northeast side of the
volcano, much smaller than Mount St. Helens but just as effective in
obliterating everything in its path. The photo below at left shows the area in
August, 1968. Note the new snow on the summit. At right is the same scene
in June 2003 from almost exactly the same vantage point. Note that there is a lot
of snow still here in June. Note also that the area is mostly revegetated.

Left
and below are additional views of Mount Lassen from the (formerly)
Devastated Area

Note
that although the area is revegetating nicely, the trees are uniform in age
and size.

The Hot Rock

The
1914-15 eruptions of Mount Lassen produced little new magma. What little
there was mostly remained in the vent. One exception was this large boulder.

"Lurching
and hissing, this 300 ton chunk of lava was swept down the side of Mount
Lassen by a massive mudslide.

On May 19, 1915, molten lava welled up within Summit Crater, quickly
melting the deep snow pack on the side of the peak and triggering an
avalanche of slush and rocks.

This huge boulder was still scalding hot 40 hours after its wild, 5 mile
ride."

Close
up of the porphyritic dacite of the boulder.

Chaos Jumbles

Chaos
Crags, in the background, are a series of lava domes. The outer crust
spalled off and spilled outward as landslides, covering much of the adjacent
area with boulder fields.

Manzanita Lake

This is the viewpoint for Mount Lassen.

Distant View

A late afternoon view from the south, showing that Mount Lassen is
built on the base of a former much larger volcano.